The present invention relates to an antenna for radio communication terminal apparatus connected to information processing apparatus such as a personal computer and a personal digital assistant (PDA), adapted to reduce a high-frequency noise component entering the high-frequency circuit of the radio communication apparatus, the noise component originating from the control circuit of information processing apparatus such as a personal computer or a PDA.
Conventionally, it was a customary practice to use a xc2xcxcex to xe2x85x9cxcex whip antenna as an antenna for radio communication terminal apparatus where a high-frequency circuit, a communication control circuit and an antenna were integrated.
FIG. 5 shows a configuration of radio communication terminal apparatus that uses a conventional xc2xcxcex whip antenna. In the radio communication terminal apparatus, a circuit board 141 is composed of a high-frequency circuit 139 and a communication control circuit 140, and the antenna portion is integrated by connecting the high-frequency circuit 139 and the xc2xcxcex whip antenna 135.
A xc2xcxcex to xe2x85x9cxcex whip antenna requires a favorable ground for operation as an antenna. For radio communication terminal apparatus that requires a compact design generally uses the ground for the circuit board 141 also as a ground operating as an antenna radial.
However, the conventional xc2xcxcex to xe2x85x9cxcex whip antenna requires a broad and stable ground surface in order to obtain stable characteristics.
Conventionally, the ground surface of a circuit board also plays the role of an antenna ground for radio communication terminal apparatus that requires a compact design. Further downsizing is under way in recent radio communication terminal apparatus. This makes it difficult to provide a sufficiently stable and wide antenna ground.
For a one-piece design comprising a high-frequency circuit and a communication control circuit in radio communication terminal apparatus shown in FIG. 5, there is a problem that, in case the role of an antenna ground is played by the ground for the communication control circuit, a high-frequency noise component enters the high-frequency circuit via the ground for the circuit board, the noise component originating from the communication control circuit of the radio communication terminal apparatus.
Also in case radio communication terminal apparatus is connected to information processing apparatus such as a personal computer and a PDA, there is a problem that a high-frequency noise component enters the high-frequency circuit via the ground for the radio communication apparatus, the noise component originating from the control circuit of the information processing apparatus.
Thus, in case a high-frequency component noise originating from the control circuit is a noise signal whose frequency is the same as the receiving frequency in radio communication terminal apparatus, there arises a problem of a cochannel suppression interference.
The invention solves the problem and aims at providing an excellent antenna for radio communication terminal apparatus that can reduce a high-frequency noise component entering the high-frequency circuit via ground for the circuit board, the noise component originating from the control circuit and having the same frequency as the receiving frequency in the radio communication terminal apparatus, without impairing antenna characteristics.
The first aspect of the invention is an antenna for radio communications apparatus, in that separate matching circuits are provided for an extended antenna and a housed antenna and a ground for a circuit board is separated from a ground operating as an antenna radial in order for the length of the antenna operates at xc2xdxcex both when the antenna is housed and when it is extended thus preventing high-frequency currents of the antenna from flowing into information processing apparatus via the ground for the circuit board, and that the electrical operation length of the antenna is arranged outside the information processing apparatus in order to place a noise source at a distance from the current loop of the antenna.
Via this configuration, it is possible to reduce a high-frequency noise component entering the high-frequency circuit via the ground for the circuit board, the noise component originating from communication control circuit, without impairing antenna characteristics.
The second aspect of the invention is an antenna for radio communications apparatus according to the first aspect of the invention, in that plural stage rods are used as antenna elements.
Via this configuration, the antenna operates the same way as the first aspect of the invention when the antenna is extended and the antenna set can be made compact by telescoping the rods.
The third aspect of the invention is an antenna for radio communications apparatus according to the first aspect of the invention, in that the antenna is configured to be xc2xcxcex whip+xc2xcxcex radial both when the antenna is extended and housed.
Via this configuration, by making the antenna length xc2xdxcex, it is possible to reduce a high-frequency noise component entering the high-frequency circuit, the noise component originating from communication control circuit, without letting excessive high-frequency currents flow on a circuit board.
The fourth aspect of the invention is an antenna for radio communication terminal apparatus according to any of the first through third aspects of the invention, in that the electrical length corresponding to xc2xcxcex whip when the antenna is housed is a helical type.
Via this configuration, by making the electrical length corresponding to xc2xcxcex whip a helical type, an antenna set can be downsized when it is housed.
The fifth aspect of the invention is an antenna for radio communication terminal apparatus according to any of the first through third aspects of the invention, in that the electrical length corresponding to xc2xcxcex radial is a helical type.
Via this configuration, by making the electrical length corresponding to xc2xcxcex radial a helical type, an antenna set can be downsized when it is housed.
The sixth aspect of the invention is an antenna for radio communication terminal apparatus according to any of the first through third aspects of the invention, in that the electrical length corresponding to xc2xcxcex whip when the antenna is housed and to xc2xcxcex radial is a helical type.
Via this configuration, by making the electrical length corresponding to xc2xcxcex whip when the antenna is housed and to xc2xcxcex radial a helical type, an antenna set and an antenna ground can be downsized.
The seventh aspect of the invention is an antenna for radio communication terminal apparatus according to first aspect of the invention, in that the antenna operates at xc2xcxcex helical+xc2xcxcex radial when it is housed and at xc2xdxcex whip when it is extended.
Via this configuration, by feeding power at the lowest end of xc2xdxcex whip, the current loop of the antenna can be placed at a distance from the noise source, thus reducing a high-frequency noise component entering the high-frequency circuit, the noise component originating from the communication control circuit.
The eighth aspect of the invention is an antenna for radio communication terminal apparatus according to first aspect of the invention, in that the antenna operates at xc2xcxcex helical+xc2xcxcex radial when it is housed and at xc2xdxcex helical when it is extended.
Via this configuration, by feeding power at the lowest end of xc2xdxcex helical, the current loop of the antenna can be placed at a distance from the noise source, thus reducing a high-frequency noise component entering the high-frequency circuit, the noise component originating from the communication control circuit.
Also, by making the length of the antenna when it is extended xc2xdxcex helical, the antenna set when it is extended can be shortened.
The ninth aspect of the invention is an antenna for radio communication terminal apparatus according to first aspect of the invention, in that the antenna operates at xc2xdxcex whip both when it is housed and extended.
Via this configuration, a matching circuit can be used in common both when the antenna is housed and extended.
The tenth aspect of the invention is an antenna for radio communication terminal apparatus according to first aspect of the invention, in that the antenna operates at xc2xdxcex helical both when it is housed and extended
Via this configuration, a matching circuit can be used in common and the antenna set can be downsized both when the antenna is housed and extended.
The eleventh aspect of the invention is an antenna for radio communication terminal apparatus according to first aspect of the invention, in that a mechanical contact is used for switching between the two states, when an antenna is extended and when it is housed.
Via this configuration, antenna elements can kept in contact by a spring contact. This facilitates switching between the two states, when an antenna is extended and when it is housed, without increasing current consumption.
The twelfth aspect of the invention is an antenna for radio communication terminal apparatus according to first aspect of the invention, in that a micro-switch and a high-frequency switch IC are used for switching between the two states, when an antenna is extended and when it is housed.
Via this configuration, separate matching circuits can be switched between the two states, when an antenna is housed and when it is extended.